Topology question regarding circular holes
For a game engine, use triangles. Most game engines do not support ngons anyway, and the ones that do are just converting the ngon to triangles.

In general modeling, you should try to avoid triangles and ngons (there are some cases where they are ok), however when modeling for a game, low poly takes precedent over nice topology, so triangles are normal.

In your case, even if it was not a game model, I would not want a ngon in the middle of the model. Ngons have a nasty way of deforming a model, and any ngon that is not perfectly flat will cause shading artifacts.

What is the technical difference between an Ngon and a bunch of Tri&#39;s?
When should N-Gons be used, and when shouldn&#39;t they?